title: Fas expression on antigen-specific T cells has costimulatory, helper, and down-regulatory functions in vivo for cytotoxic T cell responses but not for T cell-dependent B cell responses.
abstract: Fas-mediated apoptosis is an important contributor to contraction of Ag-driven T cell responses acting only on activated Ag-specific T cells. The effects of targeted Fas deletion on selected cell populations are well described however little is known regarding the consequences of Fas deletion on only activated Ag-specific T cells. We addressed this question using the parent-into-F(1) (P-->F(1)) model of acute or chronic (lupus-like) graft-vs-host disease (GVHD) as a model of either a CTL-mediated or T-dependent B cell-mediated response, respectively. By transferring Fas-deficient lpr donor T cells into Fas-intact F(1) hosts, the in vivo role of Ag-specific T cell Fas can be determined. Our results demonstrate a novel dichotomy of Ag-specific T cell Fas function in that: 1) Fas expression on Ag-activated T cells has costimulatory, helper, and down-regulatory roles in vivo and 2) these roles were observed only in a CTL response (acute GVHD) and not in a T-dependent B cell response (chronic GVHD). Specifically, CD4 T cell Fas expression is important for optimal CD4 initial expansion and absolutely required for help for CD8 effector CTL. Donor CD8 T cell Fas expression played an important but not exclusive role in apoptosis and down-regulation. By contrast, CD4 Fas expression played no detectable role in modulating chronic GVHD induction or disease expression. These results demonstrate a novel role for Ag-specific T cell Fas expression in in vivo CTL responses and support a review of the paradigm by which Fas deficiency accelerates lupus in MRL/lpr lupus-prone mice.
authors.affiliation: Department of Pathology, Uniformed Services University of Health Sciences, Bethesda, MD 20814, USA.
authors.forename: Irina
authors.initials: I
authors.lastname: Puliaeva
authors.forename: Roman
authors.initials: R
authors.lastname: Puliaev
authors.forename: Andrei
authors.initials: A
authors.lastname: Shustov
authors.forename: Mark
authors.initials: M
authors.lastname: Haas
authors.forename: Charles S
authors.initials: CS
authors.lastname: Via
mesh_terms: D000208:Acute Disease; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000637:transplantation; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003433:Crosses, Genetic; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000008:administration & dosage / Q000276:immunology*; D006086:Graft vs Host Disease / Q000235:genetics / Q000276:immunology / Q000401:mortality; D008181:Lupus Nephritis / Q000235:genetics / Q000276:immunology / Q000473:pathology; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism / Q000637:transplantation; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism; D019014:fas Receptor / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology
chemical_list: D018984:Epitopes, T-Lymphocyte; D019014:fas Receptor